Carburetor



March 17, 19316.

Filed Jan. 17, 1935 y. R. HEFTLER 2,034,097 f Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE 12 Claims.

This invention relates to carburetors for eX- plosion engines, and more particularly to a novel construction of means to deliver an additional amount of liquid fuel during the action of opening the throttle.

It has been customary for sometime to provide carburetors with means to supplement the normal fuel delivery with an additional and temporary fuel delivery upon the opening of the throttle. One of the purposes of this invention is to provide an improved construction whereby the delivery of this additional amount of fuel begins with maximum force upon opening of the throttle and continues with a decreasing force for an appreciable time thereafter, so that, even if the throttle is o-pened quickly and completely, the delivery of such additional amount of fuel will continue after'the throttle has come to rest in an open position so'as to last for an appreciable length of time until the motor has gone successfully through the early stages of acceleration, at which stages the engine is liable to miss, and perhaps stop altogether, unless some additional amount of fuel is furnished.

Another purpose of'this invention is to provide Y aV thermostatic control of this additional fuel delivery. The appended drawing shows in schematic form an `embodiment of this invention; Fig. 1 shows in section a conventional downdraft carburetor with my improved acceleration system, with the parts shown in the idling position, that ls to say with the throttle nearly closed; Fig. 2 shows the position of the parts of the accelerating system after throttle has been opened. Fig. 3 shows separately the construction of a piston and its piston'rod.

The carburetor comprises a mixture conduit II formed at I2 into a Venturi shape and comprising a secondary venturi I3 into which the main fuel nozzle I4 projects to deliver fuel to the air stream in accordance with the suction of the engine. The customary throttle I5 is provided to regulate `the effective cross-area of the mixture conduit II and cooperates with an idling fuel delivery I6. Both the nozzle I4 and the idling fuel delivery I6 are fed through channel I1 from a fuel reservoir I8 in which the fuel level is maintained at a predetermined level by a float I9 cooperating with a needle valve 2l controlling the outlet of the fuel feed pipe 22. All the above parts andthe arrangement thereof are well-knownr in the art, their mode of operation well understood, and further description is therefore unnecessary. For the purpose of acceleration, I provide two rod 36 by suitable means, such as pin 4I.

pump cylinders 23 and 24, connected by aperture y 25 and provided with an intake valve 26 and a delivery valve 21. A conduit 28, controlled by said delivery valve 21, brings the fuel delivered by the two pumps 23 and 24 to an accelerating f nozzle 29. 1

In the pump cylinders are located pistons 3| and 32, constructed in a similar manner, so that the description of piston 32 will apply to piston 3 I. Piston 32 is in the shape of a hollow cylinder, like an inverted thimble, having a bore 33; the head of the piston is provided with a hole 34 of smaller diameter than bore 33 which is closed at the opposite end by suitable means, such as, for instance, a solid plate 35 over which the metal of the piston has been turned. A piston rod 36 provided with an enlarged head 31 has been inserted through bore 34 before the securing of closure 35 has been eifected; a helical compression spring 38 encircles the piston rod 36, and is maintained in compression against the head of the piston by a retaining member, such as cup 39, secured in position on the piston The piston rod 36 is bent at right angle at 42 to form a horizontal portion 43 suitable for insertion in a hole 44 provided in a walking beam 45 which is actuated coincidentally with the throttle as follows.

As shown in Fig. 1, hole 44 is made with two horizontal key slots, and as shown in Fig. 3, the horizontally turned portion 43 of piston rod 36 is stamped so as to provide two vertical lugs, or keys, such as 53. To assemble the two parts, the piston rod, with its spring and piston, is held horizontally so that key 53 can be inserted in the key slot and when this is done and the piston rod turned so that the piston can be inserted in the pump cylinder, it will be seen that the parts are safe against accidental separation.

The throttle I5 is actuated by a lever 46 having a branch 41 connected by link 48 to a vertical portion 49 of walking beam 45 which may slide `in suitable grooves 5I and 52. In this manner, when the throttle is opened the Walking beam 45 is brought in the position of Fig. 2 and the pistons 3| and 32 are actuated downward, putting a pressure on the liquid fuel contained in the two communicating pump cylinders 23 and 24. This pressure closes the intake valve 26 so that the fuel is ejected past delivery valve 21 through conduit 28 and accelerating nozzle 29.

The piston 3| is, like piston 32, threaded on a headed piston rod 56 and a spring 58 is inserted between the head of the piston and a retainer spring cut similar to cupV 39. A hollow boss 6| projects downwardly from the fuel reservoir cover 62 to afford a stop for piston 3| so that it shall be unable to assume a position higher than the one shown in Fig. 1.

The piston 3| is provided with a groove into which is tted a piston ring 55 made of thermostatic metal, so that it will tend to assume a larger diameter when warm than when cold.

It is to be noted that, in order to obtain the desired result, the two springs are made of different characteristics, spring 38 being stiffer so as to give very little, if at all, when the walking beam 45 is depressed.

The operation is as follows: Upon even a slight opening of the throttle, walking beam 45 is depressed and carries with it the two piston rods 36 and 56, which move downwardly within the pistons 3| and 32, thus compressing the springs 38 and 58. Because of the connection 25 between the two pump cylinders 23 and 24, the liquid in both cylinders will be under the sam'e pressure, but due to the difference in the force of springs 58 and 38, the weaker of the two, namely spring 58, will shorten up more'readily than the stronger spring 38; piston 3| might move upward, were it not prevented from doing so by the hollow boss 6|, with which it comes in contact.

At the beginning of the pumping action piston 32 will be pushed downward by the force of spring 38 and fuel will be at once ejected through nozzle 29 while piston 3| remains in contact with the hollow boss 6|. When, in this downward movement of piston 32, spring 38 has lengthened sulficiently so that the force it exerts is no longer superior to the force exerted by the compressed spring 58, the piston 3| begins its downward movement.

Spring 38 is preferably given a certain initial compression so that the pumping action will begin immediately upon an even slight movement 0f the throttle. As explained above, the piston 3| will not begin its downward stroke until after piston 38 has travelled downward to a certain extent. The initial compression of springs 38 and 58 and the design of the springs m'ay be selected so that there will be a great difference in the action of the two pump cylinders with the effect that the duration of the pumping action will be quite longer than where only a single pump is employed. It will also be plain that the rate of fuel delivery by the piston 3| will be materially less than the rate of fuel delivery by piston 32, so that the end of the pumping action is gradual.

However, should the temperature be high, the piston ring 52 tends to assume a greater diameter so as to create a friction on the pump cylinder and to impede the downward movement of piston 3| according to temperature. The advantage of reducing the accelerating charge when the temperature is high is well understood.

Closure of the throttle will reverse the operation and raise the pistons to the position shown in Fig. 1, whereupon fuel will be drawn into the pump cylinders through the intake valve 26 and the apparatus will be in required condition for subsequent acceleration.

I claim:

1. In a carburetor, a throttle, a pump actuating member connected thereto, a pair of accelerating pumps, each comprising a bore with a hollow piston therein, each of said pistons having an apertured head, an open foot and a closure for said foot, a pair of shouldered rods, each engaging one of said piston heads to form a oneway connection therewith and fulcrumed at their other ends on the aforementioned pump actuating member, a pair of springs each bearing on said piston and on a spring stop carried by said rod, one of said springs being of greater ilexibility than the other and a common delivery passage for both pumps.

2. In a carburetor, a throttle, a pump actuating member connected thereto, a pair of accelerating pumps, each comprising a bore with a piston therein, a connection between each piston and the aforementioned pump actuating member, said connections being positive in the direction of the pump filling stroke and elastically yielding in the other direction, one of said connections being of greater flexibility than the other, and means to deliver the pump discharges into the carburetor.

3. In a carburetor, a throttle, a pump actu'- ating member connected thereto, a pair of accelerating pumps, each comprising a bore with a piston therein, a connection between each piston and the aforementioned pump actuating member, said connection being positive in the direction of the pump filling stroke only, spring means to urge each of said pistons in the other direction, one of said spring means being of greater flexibility than the other, and means to deliver the pump discharges into the carburetor.

4. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, a pair of accelerating pumps, each comprising a bore with a piston therein, fuel inlet means for said pumps, outlet means for said pumps leading to the mixture passageway, means to positively actuate said pistons to ll said pump bores with fuel upon closure of the throttle, elastic means to actuate said pistons to force fuel through said outlet means upon opening the throttle, one of said elastic means being of greater flexibility than the other.

5. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, a pair of accelerating pumps, each comprising a bore with a piston therein, fuel inlet means for said pumps, outlet means for said pumps leading to the mixture passageway, means to positively actuate said pistons to fill said pump bores with fuel upon closure of the throttle, elastic means to actuate said pistons to force fuel through said outlet means upon opening of the throttle, one of said elastic means being of greater flexibility than the other, and thermostatic means to modify the rate of motion of one of said pistons when actuated by its associated elastic actuating means.

6. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, a pair of accelerating pumps, each comprising a bore and a piston therein, fuel inlet means for said pumps, outlet means for said pumps leading to the mixture passageway, means to positively actuate said pistons to ll said pump bores with fuel upon closure of the throttle, elastic means to actuate said pistons to force fuel through said outlet means upon opening of the throttle, one of said elastic means being of greater flexibility than the other, and means to limit the travel of the one piston associated with the weakest elastic actuating means in the direction of the filling stroke.

7. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, a pair of accelerating pumps, each comprising a bore and a piston therein, fuel inlet means for said pumps, outlet means for said pumps leading to the mixture passageway, means to positively actuate said pistons to ll said pump bores with fuel upon closure of the throttle, elastic means to actuate said pistons to force fuel through said outlet means upon opening of the throttle, one of said elastic means being of greater flexibility than the other, and a thermostatic piston ring on one of said pistons.

8. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, an accelerating pump comprising a bore with a piston therein, fuel inlet means for said pump, outlet means for said pump leading to the mixture passageway, means to positively actuate said piston to fill said pump bore with fuel upon closure of throttle, elastic means to actuate said piston to force fuel through said outlet means upon opening of the throttle, and thermostatic means to increase the frictional resistance to the movement of the piston as the temperature increases.

9. In a carburetor having a mixture passageway, a fuel supply chamber, a throttle, and an accelerating pump chamber, a pump actuating member, means to actuate said pump actuating member upon opening of the throttle, a hollow piston for said pump, a piston rod adapted to slide freely into an opening in the head of said piston, a retaining shoulder at one end of said piston rod, a closure for the other end of said piston, a spring surrounding said piston rod and means on said piston rod to form a stop for said spring, said piston rod being bent at the other end, the bent portion having a part of its length formed in a non-circular cross-section, an aperture in said pump actuating member of substantially the same non-circular cross-section but having an orientation materially different from the orientation of the non-circular cross-section of the piston rod when the latter is in assembled Working position.

10. In a carburetor having a mixture passageway and a fuel supply chamber, a throttle, an accelerating pump comprising a chamber of variable volume, a fuel inlet means therefor, outlet means leading from said chamber to the mixture passageway, means to actuate said pump to ll said pump chamber with fuel upon closure of the throttle, elastic means to actuate said pump to force fuel through said outlet means upon opening of the throttle, and thermostatic means to increase the frictional resistance to the actuation of the pump as the temperature increases.

11. In a carburetor, an accelerating pump having resilient operating means and thermostatic means to increase the frictional resistance to the movement of said pump as the temperature increases.

12. In a carburetor, an accelerating pump provided with a piston, resilient means to operate said piston, and thermostatic means to increase the frictional resistance to the movement of said piston as the temperature increases.

VICTOR R. HEFTLER. 

